The invention relates to a production unit, in particular a bending press, for forming workpieces of sheet metal, having two press beams which are displaceable relative to one another by means of a drive mechanism and which can be used to obtain a desired tool length by fitting a variable number of bending tools, and having a control device connected to the drive mechanism for influencing the operating behaviour of the production unit as a function of states detected by sensors, manual control commands and/or specifications stored in a memory device, in which the inserted bending tools have machine-readable unmistakable codes in the form of electronically detectable information carriers to enable them to be identified and/or their position detected on an at least partially automated basis, and an electronic detection device provided as a means of identifying a plurality of information carriers and connected to the control device or to a control and/or evaluation device co-operating with it co-operates with the first and/or second press beam, at least one displacement and/or guide mechanism being provided, extending essentially parallel with the achievable tool length, which accommodates the detection device so that the codes or data and/or detection signals of a plurality of information carriers can be detected consecutively and can be transmitted to the control device or the control and/or evaluation device co-operating with it.
Patent specifications DE 38 24 734 A1 and DE 38 30 488 A1 disclose a production unit 1 for processing metal, in particular a die bending machine or a die forging press, with an electronic tool detection system. A set of bending tools for these units consists of at least a top tool, in particular a stamp, and a bottom tool, in particular a die. However, these tools can also be split up into segments, i.e. separated, so that the smaller tool parts are easier to handle. At least one electronically detectable code carrier is mounted in the respective individual tools, which contains all the geometric data defining the tool and the permissible tool load data. Alternatively, the code carrier may also be defined by nothing more than a tool code if the tool data is stored in the machine controller. In order to be able to read the code carriers in the tools, at least one reading head is mounted respectively in the region of the tool holder mechanisms, i.e. on the press beam and on the press table. These reading heads provided for each code carrier enable the tool data or tool codes of the individual code carriers to be detected and transmitted to the machine controller. The disadvantage of this is that it is necessary to provide a plurality of reading heads in order to detect one of a plurality of possible work tools for every bending tool, which means that a relatively complex cabling and wiring system is needed, amongst other things. In addition, situations may arise in which a new set of bending tools does not match the disposition of the reading heads because of a different pitch distance, so that either the disposition of the individual reading heads has to be changed or the positioning of the code carrier on the bending tools has to be adapted, which then requires a series of awkward manipulations.
Document DE 44 42 381 A1 discloses a device for detecting the position and shape of top cheek tools on die bending machines and die presses. Disposed behind a top cheek in a guide is a motor-driveable carriage on which a holder is mounted. Integrated in the holder is a photoelectric barrier with transmitter and receiver, which co-operates with an electronic evaluation system to determine the length of the top cheek tools fitted in the top cheek and the spaces in between them by means of reflection. Also disposed in the holder is a writing-reading head, the purpose of which is to read codes provided in code carriers in the rear face of the top cheek tools. The information is scanned by passing the writing-reading head across them and then evaluated by an electronic evaluation system.
Document EP 0 919 300 A1 discloses a bending press for forming workpieces of sheet metal, in which a press beam co-operates with a scanner which scans identification codes or symbols and a position detecting device which detects the position of the scanner. The bending press has a display device and a memory so that position-related data from the scanner and position-related data form the position detecting device can be read in conjunction with one another and stored in the memory. A top or a bottom frame is moved in a vertical direction, releasable impact dies or bending tools being disposed in the top frame. The die disposed in the bottom frame is compared with the dies in the top frame. The reading device is displaced in a guide device, horizontally with respect to the top frame, until the scanner reads an identification code or symbols. The data is read and the position-related data from the reading device is stored in the memory.